Load absorbing device

ABSTRACT

A load absorbing device or other resilient device, such as a fender, bumper, or rub rail, for protecting an object, such as a dock or boat, from an impact force delivered by another object includes a leaf spring portion connected to the object. The leaf spring portion includes a fixed end and a free end operable to transmit to the object a fraction of the impact force and is designed to collapse upon loading with the impact force to thereby absorb energy that would otherwise be transferred directly to the object. In a preferred embodiment, the leaf spring portion is extruded of a high-strength abrasion-resistant plastic material having a low coefficient of friction, such as ultra high molecular weight polyethylene (UHMWPE). The leaf spring portion may include multiple mounting holes sized to receive mounting fasteners for rigidly connecting the device to the object.

RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No. 11/236,314, filed Sep. 26, 2005, now U.S. Pat. No. 7,624,694, issued Dec. 1, 2009, which is a continuation of U.S. patent application Ser. No. 10/421,527, filed Apr. 21, 2003, now U.S. Pat. No. 6,948,440, issued Sep. 27, 2005, which is a continuation-in-part of U.S. patent application Ser. No. 10/205,861, filed Jul. 26, 2002, now U.S. Pat. No. 6,832,570, issued Dec. 21, 2004, all of which are hereby incorporated by reference in their entireties.

TECHNICAL FIELD

This disclosure relates to resilient devices, such as fenders for protecting boat hulls, docks, trains, train platforms, and various other vehicles, structures, and objects.

BACKGROUND

Fenders (also known as rub rails, rub guards, and bumpers) are commonly used to facilitate sliding and prevent damage to a boat or other vessel when rubbing or bumping against structures, such as pilings and docks. Fenders are typically attached along the hull of a boat, but may also be attached to docks, pilings, seawalls, bridge footings, and other structures against which a vessel may rub or bump. Fenders are also used to protect other objects from damage due to rubbing and bumping—especially warehouse loading docks and land vehicles, such as truck trailers.

A fender system used with many military and commercial ships includes a length of half round steel pipe (hereinafter “split pipe”) extending along the hull and welded to the outside of the hull to form a raised rib. A relatively smooth outer surface of the fender is desirable for sliding maneuvers such as docking, when the vessel is sliding along another object, such as a piling or dock. In these sliding maneuvers, any dents or discontinuities in the outer surface of the split pipe fender can inhibit a smooth sliding action by converting the desired longitudinal motion into an undesirable athwart ship motion, thereby causing the vessel to move away from the piling surface along which sliding is intended to occur. Dents in the split pipe can also cause impact loads to be concentrated at a small location on the hull, rather than dispersing loads across a relatively large area. The strength of the split pipe determines the energy absorption capability of the fender system in impact situations. When impacts occur that exceed its strength, the steel permanently deforms, leaving a dented outer surface. Such dents must be repaired to maintain a smooth sliding surface. Furthermore, the outer surface of the split pipe is typically painted and requires regular repainting and maintenance to prevent corrosion and other causes of failure, even in the absence of severe impacts.

Pleasure boats commonly have a light-duty fender system that includes strips of elastomer material seated in retainer channels or brackets along the sides of the hull. One such light-duty fender system is described in U.S. Pat. No. 2,959,146 of Erkert. Such fender systems are able to maintain a smooth sliding surface without discontinuities because the elastomer material is resilient. However, elastomer materials have a higher coefficient of friction than painted steel. Consequently, elastomer fenders do not slide as easily as split pipe fenders. Friction effects become even more pronounced when the elastomer is compressed, as during high impact conditions. The elastomer material also has limited abrasion resistance. In certain situations, the elastomer can be pulled out of its retainer, thereby making the fender system ineffective. Such fender systems also have a lower impact absorption capability than split pipe fender systems, and can allow impact forces to be transferred to the hull and cause damage.

U.S. Pat. No. 4,084,533 of Boyer describes a reversible rubrail for boats and ships that is formed of a unitary strip of extruded rubber or flexible plastic material. The rubrail includes a rear wall for connection to a boat and a pair of front walls extending from top and bottom edges of the rear wall in an arcuate shape to overlap along free ends of the front walls. The front walls are flexible and can be folded back to allow screws, bolts, or staples to be inserted through the rear wall for installation of the rubrail. Because the material of the front walls must be soft enough to be manually folded back for installation, the rubrail of Boyer would also suffer from the high coefficient of friction and low abrasion resistance of conventional elastomer strip fender systems.

The present inventor has recognized a need for a fender that can absorb a substantial amount of energy, that is highly resistant to permanent deformation and abrasion, has a low coefficient of friction, is easily installed, and requires little or no maintenance.

SUMMARY

According to one embodiment, a bumper comprising a member is connected to a surface of a first object to thereby protect the first object from damage due to a force applied by a second object. The member has a proximate portion rigidly connected to the first object. The proximate portion extends away from the first object and transitions into a middle portion substantially parallel to the surface of the first object. The middle portion transitions into a distal portion. The distal portion extends toward the first object and terminates at a free end. The member thereby defines a compression space between the first object and the member and is operable to collapse into the compression space when the second object applies a force to the member. The middle portion has a front side facing the second object and the front side has a low coefficient of kinetic friction when the second object slides against the middle portion.

According to another embodiment, a rub rail comprising a curved member and compression space is mounted to a first object to thereby protect the first object from damage due to a force applied by a second object. The curved member has a fixed end rigidly secured to the first object and a free end opposite the fixed end. The fixed end and the free end are operable to transmit a fraction of the force from the second object to the first object. The compression space is defined by the curved member and the first object and into which at least a portion of the curved member enters when the second object applies a force to the curved member. The curved member has a contact area defined by the portion of the second object that touches the curved member during operation and the member is configured such that the contact area increases as a portion of the curved member enters the compression space. The curved member is formed from a material having a low coefficient of kinetic friction as the second object slides along the curved member.

According to yet another embodiment, a load absorbing device comprises a curved member for mounting to a first object. The curved member has a fixed end rigidly connected to the first object and a free end opposite the fixed end. The curved member has a contact area to absorb a load delivered by a second object and the contact area increases when under load to thereby more evenly distribute the load between the curved member and the second object. The curved member is formed from a material having a low coefficient of kinetic friction when the second object is in contact with and moves relative to the curved member.

Additional aspects and advantages will be apparent from the following detailed description of preferred embodiments, which proceeds with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a corner of a dock to which is mounted a fender in accordance with a first embodiment;

FIG. 2 is a perspective view of a fender in accordance with the first embodiment, shown mounted to the hull of a boat;

FIG. 3 is a front elevation view of the fender of FIG. 1;

FIG. 4 is an enlarged cross section view of the fender of FIG. 1, taken along line 4-4 of FIG. 3;

FIG. 5 is a front elevation view of a fender in accordance with a second embodiment, mounted to the side of a dock;

FIG. 6 is a cross section view of the fender of FIG. 5, taken along line 6-6 of FIG. 5;

FIG. 7 is a cross section view of the fender of FIG. 5, taken along line 7-7 of FIG. 5;

FIG. 8 is a cross section view of a third embodiment fender; and

FIGS. 9, 10, 11, and 12 are cross section views of fenders having removably attached leaf spring portions in accordance with respective fourth, fifth, sixth, and seventh embodiments.

In the figures, like reference numerals represent the same or similar parts or features.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

A fender for protecting a vehicle or object from damage includes a mounting portion and a resilient leaf spring portion connected to the mounting portion. The mounting portion and the leaf spring portion together form a compact spring having a generally P-shaped cross section. In one embodiment, the mounting portion and the leaf spring portion are integrally formed in a unitary one-piece structure by extrusion of a high-strength abrasion-resistant plastic material having a low coefficient of friction and a high impact resistance, such as an ultra high molecular weight polyethylene. In another embodiment, the leaf spring portion is removably connected to the mounting portion to allow the leaf spring portion to be replaced, when necessary.

The mounting portion of the fender includes a rear side for mounting to the object or vehicle, and a front side opposite the rear side. The mounting portion preferably includes multiple mounting holes, which may be drilled after extrusion and which are sized to receive screws or bolts for attaching the fender to an object or vessel.

The resilient leaf spring portion projects outwardly from a joint region and along the front side of the mounting portion to span over at least part of the front side. The distal end of the leaf spring portion is free to slide along the front side of the mounting portion when the leaf spring portion flexes under load. The leaf spring portion may include multiple access holes in alignment with the mounting holes of the mounting portion. The access holes admit a tool, such as a socket wrench or screwdriver, for tightening fasteners used to attach the fender to an object or vessel via the mounting holes.

Preferably the mounting portion of the fender is backed by a layer of elastomeric material interposed between the rear side of the mounting portion and the object or vessel, to provide further dampening and load distribution. Pigments or additives may be added to the plastic material to improve the fender's appearance and/or resistance to ultraviolet radiation. The surfaces of the plastic material may be textured or otherwise treated to impart radar scattering or absorbing properties desirable when the fender is used on military ships or other military equipment. In one embodiment, the fender is provided with a flat upper surface on an outer portion of the fender along the joint region, which can be aligned with the upper edges of a boat deck or dock to increase the usable area of the deck or dock. A high-friction traction material may be embedded in the flat upper surface to enhance safety by reducing slippage at the edges of the deck or dock.

FIG. 1 is a partial fragmentary view of a fender 10 in accordance with a first preferred embodiment shown mounted to a dock 12. FIG. 2 shows fender 10 mounted to a hull 18 of a boat 20. Although FIGS. 1 and 2 show use of fender 10 in a marine setting, those skilled in the art will understand that fender 10 has utility in any environment or application where there is a need to protect an object from damage due to collisions with another object, regardless of whether one of the objects is stationary. For example, fenders in accordance with the various embodiments described herein are also useful for delivery trucks and vans, warehouse loading docks, automobiles, trains, train platforms, subway cars, subway platforms, pushcarts, walls, seawalls, bridge footings, locks, and any other vehicles, objects, structures, and environments in which collisions are common and in which, if not protected, the objects are subject to damage during collisions. For convenience, and without limiting the scope of the invention, the following description of preferred embodiments proceeds with reference to use of fenders in a marine environment and, specifically, in connection with a boat or dock, as shown in FIGS. 1 and 2.

FIG. 3 is a front elevation view of fender 10 mounted to dock 12. FIG. 4 is an enlarged cross section view of fender 10 taken along line 4-4 of FIG. 3. With reference to FIGS. 3 and 4, fender 10 includes a mounting portion 30 and a leaf spring portion 40 integrally formed of a unitary, one-piece construction. Mounting portion 30 is preferably an elongate planar strip having a rear side 32 that faces toward dock 12 and a front side 34 opposite rear side 32 and facing away from dock 12. Fender 10 may be flexible enough along its length to conform to a slightly curved shape such as hull 18 (FIG. 2) when mounted thereto. Alternatively, fender 10 and/or mounting portion 30 may be shaped to conform to an irregularly-shaped object (not shown), for example by heating and bending, molding, or other fabrication or machining methods known in the art. Fender 10 may also be made in shapes that are not elongate strips, such as round shapes, for example (not shown).

Mounting portion 30 includes multiple mounting holes 42 extending through its thickness “t” and spaced apart along the length of fender 10. Mounting holes 42 are sized to receive a mounting fastener 48, such as a bolt or screw. Each of the mounting holes 42 preferably includes a countersink or a counterbore 52 that is deep enough so that a head or nut 54 of mounting fastener 48 does not protrude above an outer surface 58 of front side 34, thereby preventing damage to mounting fasteners 48 and the underside of leaf spring portion 40. The thickness t of mounting portion 30 will typically be dictated by the size of the bolt head or nut 54 and the thickness of material of the mounting portion 30 required to securely fasten fender 10 to dock 12 (i.e., material clamped between the head or nut 54 and dock 12). However, other considerations such as flexibility, expected loads, durability, and aesthetics may also be considered when determining thickness t of mounting portion 30. For example, thickness t may be in the range of approximately 0.25 inch (0.64 cm) for small craft to approximately 2.0 inches (5.1 cm) or more for large vessels. A preferred thickness t for seagoing vessels is approximately 1.0 inch (2.5 cm). The height of mounting portion 30 will be proportional to thickness t. At 1.0 inch (2.5 cm) thickness, mounting portion 30 would preferably have a height of approximately 6.0 inches (15.2 cm), for example. The length of mounting portion 30 will be sized to fit the length of dock 12 or boat 20 on which it will be used.

Leaf spring portion 40 projects outwardly from front side 34 of mounting portion 30 and downwardly to extend over mounting holes 42 and then back toward front side 34 of mounting portion 30 to terminate in a free end 66. The shape of leaf spring portion 40 defines a compression space 70 located between leaf spring portion 40 and front side 34 of mounting portion 30. Leaf spring portion 40 and free end 66 preferably extend along the length of fender 10 but may extend along only a portion thereof. A slit 68 divides mounting portion 30 and free end 66. By extending over mounting holes 42, leaf spring portion 40 tends to hide mounting fasteners 48, providing an aesthetically pleasing appearance. Leaf spring portion 40 includes multiple access openings 76 that are aligned with mounting holes 42 and sized large enough to admit a tool (not shown), such as a screwdriver or socket wrench, for tightening or loosening mounting fasteners 48, thereby facilitating installation and removal of fender 10 from dock 12.

Fender 10 is formed of a resilient material that is flexible enough to allow leaf spring portion 40 to collapse into compression space 70 upon impact with an impacting object (not shown) or other applied force “F” directed toward dock 12. However, leaf spring portion 40 is rigid enough, due to its wall thickness and the elasticity of the material from which it is made, such that it is not feasible to manually bend leaf spring portion 40 away from mounting portion 30 to expose mounting fastener 48. Consequently, access openings 76 are particularly helpful for facilitating installation when mounting holes 42 are located beneath leaf spring portion 40, as in the embodiments shown in the figures. Alternatively, mounting fasteners 48 could be located in an uncovered location, for example, along one or more flanges that could extend beyond leaf spring portion 40 (not shown). The phantom lines in FIG. 4 show leaf spring 40 in a compressed position 40 a, with free end 66 a tilted outwardly from front side 34. Leaf spring portion 40 is preferably shaped as an elliptic semi-cylinder when in an unloaded condition, but can also be formed in any other shape suitable for collapsing upon application of an impact force, such as semi-cylindrical, semi-ellipsoid, hemispherical, and trapezoidal, for example.

Leaf spring portion 40 connects to mounting portion 30 at a common joint section 80. Joint section 80 preferably extends along top edge 84, and leaf spring portion 40 extends downwardly therefrom. However, fender 10 could alternatively be oriented so that joint section 80 extends along a bottom or side edge of fender 10, with leaf spring portion 40 extending upwardly or laterally therefrom (not shown). The preferred orientation shown in FIGS. 3 and 4, with joint section 80 located along top edge 84, prevents water and debris from collecting inside compression space 70. To provide substantial spring action joint section 80 preferably has a thickness comparable to the thickness t of mounting portion 30 and the thickness of leaf spring portion 40, but may be substantially thinner or thicker than mounting portion 30 and leaf spring portion 40 depending on the end use of fender 10.

Joint section 80 may be integral with mounting portion 30 and leaf spring portion 40 of fender 10, as shown in FIGS. 3-8. In embodiments described below with reference to FIGS. 9-12, joint section 80 can be decoupled and is not integrally formed of one piece construction with the leaf spring and mounting portions.

Joint section 80 and leaf spring portion 40 are sized so that upon application of impact force F (including rubbing or docking-related loads), leaf spring portion 40 will collapse into compression space 70, as indicated by collapsed position 40 a. At the same time, free end 66 remains free to slide downwardly along front side 34 of mounting portion 30 and wipe against front side 34, as indicated by position 66 a. The curved, P-shaped configuration of fender 10 allows a substantial amount of energy of impact to be absorbed in flattening of leaf spring portion 40 rather then being transferred directly to dock 12. Concurrently, the ability of free end 66 to slide over front side 34 of mounting portion 30 maintains the spring action of fender 10 even under sustained impact forces or loads F. In this regard, the interface at slit 68 between free end 66 and front side 34 of mounting portion 30 should have a very low coefficient of friction to promote sliding. In addition, leaf spring portion 40 is desirably made of a material that is resistant to permanent deformation.

The amount of energy absorbed will be a function of the thickness of leaf spring portion 40 and compression space 70, which are selected based on an assumed mass and impact velocity. For example, leaf spring portion 40 may have a thickness ranging between approximately 0.25 inch (0.64 cm) for small craft to approximately 2.0 inches (5.1 cm) or more for larger vessels. The thickness of compression space 70 may range between approximately 0.42 inch (1.07 cm) and approximately 3.4 inches (8.6 cm) or more for small and large craft, respectively. A preferred thickness of leaf spring portion 40 is 1.0 inch (2.5 cm) and a preferred thickness of compression space 70 is 1.7 inches (4.3 cm) for average size vessels.

Fender 10 is preferably extruded of a durable plastic material having a low coefficient of sliding friction, high abrasion resistance, and high strength characteristics, particularly modulus of elasticity (Young's modulus), tensile yield strength, and impact strength, such as a crystalline polyolefin resin. A suitable material is ultra high molecular weight polyethylene (UHMWPE), for example of the type sold under the trade name GUR™ by Ticona LLC of Summit, N.J., USA, a division of Celanese AG and specified by ASTM D4020. While other materials and fabrication techniques can also be used in the manufacture of fender 10, UHMWPE has a combination of physical properties including abrasion resistance, strength, low friction, moldability, and resistance to permanent deformation, that are superior to any other material presently known to the inventor. Extrusion is a particularly efficient and inexpensive fabrication technique for the elongate P-shape of fender 10. Co-extrusion of two or more materials can also be used to achieve different mechanical properties at different parts of fender 10.

The combination of the compact P-shape and the resilient plastic material allows leaf spring portion 40 to collapse upon loading with impact force F, thereby absorbing energy that would otherwise be transferred directly to dock 12 or boat 20. Resistance to permanent deformation also provides a spring action that tends to reflect the absorbed energy and hold apart colliding objects, which is especially useful in the context of a docking maneuver. Leaf spring portion 40 is preferably tough enough to withstand substantially complete compression against mounting portion 30 without undergoing any significant permanent deformation. As shown in FIGS. 1 and 4, an elastomeric layer 92 is provided between mounting portion 30 and dock 12 to dissipate and distribute impact loads, rather than concentrate them at a point on dock 12. Similarly, elastomeric material can be interposed between fender 10 and hull 18 of boat 20 (not shown). A preferred elastomer strip 92 is formed of UV stabilized outdoor marine grade rubber having a hardness of approximately 65 durometer. In the event that impact forces F are great enough to cause substantially complete compression of leaf spring portion 40 and maximum elastic deformation of elastomer strip 92, fender 10 will continue to absorb impact energy by permanently deforming at the location of impact, thereby further protecting dock 12 or boat 20 from damage.

The preferred embodiments are also characterized by a low coefficient of kinetic friction, which allows fender 10 to easily slide against another object. For example, boat 20 can easily slide against a piling (not shown) and boat hull 18 can easily slide against fender 10 of dock 12. Preferably the plastic material of fender 10 has a coefficient of kinetic friction against dry polished steel of less than about 0.3. However, coefficients of kinetic friction (against dry polished steel) which are as low as possible or as high as 0.5 would also be within the scope of the present invention. Plastic materials that are useful with the preferred embodiments will typically have a coefficient of sliding friction against dry polished steel of greater than 0.05 and less than 0.5. Those skilled in the art will understand that friction characteristics are highly dependent upon the surface condition and the combination of materials that are being rubbed together. Accordingly, friction properties of fender 10 are quantified above in the context of dry polished steel for convenience only and without limiting the scope of the invention. Fender 10 may have a different coefficient of friction when sliding against materials other than dry polished steel. For example, the plastic material of fender 10 should also have a low coefficient of kinetic friction against itself (when dry) to facilitate the sliding motion of free end 66 against front side 34 of mounting portion, and preferably in the range of approximately 0.2±0.05. The low friction characteristic of fender 10 also allows the zone of compression of leaf spring portion 40 to travel easily along the length of fender 10 in the manner of a compression wave, further absorbing energy as boat 20 slides against a steel, wooden, concrete, or rubber-faced dock or piling.

As mentioned above, UHMWPE is the preferred material for use in fender 10. Other materials with some or all of the material properties of UHMWPE would also be desirable. Some physical properties of UHMWPE are set forth in the paper titled “Ultra High Molecular Weight Polyethylene (UHMWPE)”, by Harvey L. Stein published by ASM International in Volume 2 of the Engineered Materials Handbook (1999), which paper is incorporated herein by reference. For example, UHMWPE has a modulus of elasticity (Young's modulus) at room temperature of between approximately 0.6 GPa and approximately 0.8 GPa (ASTM D638 and D6712, incorporated herein by reference). UHMWPE has a tensile yield strength ranging between approximately 21.0 MPa and approximately 22.3 MPa and ultimate tensile strength ranging between approximately 46.8 MPa and 53.7 MPa. UHMWPE also has an Izod impact strength of between approximately 70 kJ/m² and approximately 220 kJ/m² (modified ASTM D256, double 15° V-notched; and ASTM D6712, incorporated herein by reference), depending on the material composition and the fabrication method used. See, e.g., “Analysis of Contemporary Resins and Conversion Methods”, ASTM Working Group for Medical Grade UHMWPE, Oct. 15, 2001, which is incorporated herein by reference. UHMWPE is also highly abrasion resistant, hydrophobic, and chemically resistant. It accepts additives, such as UV stabilizers and fire retardants, which are useful in the preferred embodiments. Pigments can also be mixed with UHMWPE to eliminate the need to paint fender 10, allowing matching of the fender's color to a boat 20 or dock 12 or for high-contrast colors and long-lasting visibility. UHMWPE can also be machined using conventional woodworking equipment, for example, to drill mounting holes 42 and access holes 76 after extrusion of mounting portion 30 and leaf spring portion 40. A miter joint 96 (FIG. 1) is another example of a shape easily obtained by conventional woodworking equipment. UHMWPE surfaces can also be textured or treated to impart radar scattering or absorbing properties desirable when fender 10 is used in a military application requiring stealth capabilities. For example, the ultrablack surface topology described in U.S. Pat. No. 5,225,933 of Myers et al., incorporated herein by reference, could be formed on or applied to outer surface of leaf spring portion 40 or other parts of fender 10. Skilled persons will appreciate that different surface textures may also be used, which are more suitable for manufacture by extrusion.

FIG. 5 shows a front elevation view of a fender 10′ in accordance with a second preferred embodiment. FIGS. 6 and 7 are cross section views taken along respective lines 6-6 and 7-7 of FIG. 5. With reference to FIGS. 5-7, fender 10′ includes a plurality of drainage openings 110 formed along free edge 66 of leaf spring portion 40′. Drainage openings 110 facilitate drainage of water from compression space 70 and further facilitate flushing or manual removal of debris that may become trapped in compression space 70.

Fender 10′ also includes multiple mounting holes 42′, which are staggered on either side of a longitudinal centerline 116 of leaf spring portion 40′. Mounting holes 42′ and, consequently, access openings 76′ are staggered so that an apex 120 of leaf spring portion 40′ is smooth and uninterrupted by access openings 76′ along the entire length of fender 10′, thereby further reducing frictional forces during sliding or rubbing of fender 10′ against another object, such as a piling. Staggering of mounting holes 42 also increases the strength and stiffness of leaf spring portion 40′ along its apex 120, as compared to fender 10 of FIG. 3.

FIG. 8 is a cross section view of a fender 10″ in accordance with a third preferred embodiment. With reference to FIG. 8, free end 66″ of leaf spring portion 40″ is normally spaced apart from front side 34 of mounting portion 30, when leaf spring portion 40″ is in an unloaded condition. This configuration leaves a gap 130 between free end 66″ and mounting portion 30 that causes leaf spring portion 40″ to act as a cantilever beam when impact forces F are initially applied to fender 10″. The cantilever beam effect can be designed to reduce the opposing reaction forces exerted against the impacting object before gap 130 is closed, thereby causing a more gradual deceleration of smaller impacting objects (not shown) relative to dock 12. Fender 10″ is, thus, capable of being flexible enough to prevent damage to smaller vessels colliding with dock 12 and, upon closing of gap 130, becoming stiff enough to also decelerate larger vessels that collide with dock 12. Gap 130 also improves drainage from compression space 70.

FIG. 8 also depicts an optional removable plug 140 positioned in access opening 76″ to seal access opening 76″ and improve the appearance of fender 10″. Fender 10″ is shown in FIG. 8 mounted flush with a top side 144 of dock 12 (or boat 20), thereby increasing the effective useable area of the top side 144. To prevent persons (and vehicles) from slipping off the top side 144, a traction enhancing material 150 is embedded in a flat upper surface 84″ of fender 10′.

FIGS. 9, 10, 11, and 12 are cross section views of fenders 10 a, 10 b, 10 c, and 10 d having leaf spring portions 40 a, 40 b, 40 c, and 40 d, respectively, detachably connected to respective mounting portions 30 a, 30 b, 30 c, and 30 d, in accordance with fourth, fifth, sixth, and seventh embodiments. With reference to FIGS. 9-12, leaf spring portions 40 a-d are connected to mounting portions 30 a-d along an upper longitudinal margin 170 of mounting portions 30 a-d, so that leaf spring portions 40 a-d can be removed for repair or replacement in the field, without requiring a new mounting portion. Fenders 10 a-d are attached to a structure 174 to be protected, such as a dock, boat, or other object. Preferably, leaf spring portions 40 a-d can be removed and replaced without detaching their corresponding mounting portions from structure 174. Leaf spring portions 40 a-d are preferably attached along the upper longitudinal margins 170. However, in alternative embodiments leaf spring portions 40 a-d may be attached to a different part of mounting portions 30 a-d, such as along a lower longitudinal margin 178, for example.

With particular reference to FIG. 9, leaf spring portion 40 a of fender 10 a includes a flange 182 a that abuts an upper side 186 of mounting portion 30 a. Flange 182 a is connected to mounting portion 30 a by means of one or more fasteners such as a screw 188 a, for example. Flange 182 a is preferably flush with a top surface of structure 174 to extend a usable topsides area of structure 174, similarly to the embodiment of FIG. 8. While the head of screw 188 a is shown in FIG. 9 as extending from the top of flange 182 a, a counterbored hole (not shown) could be provided in an alternative embodiment for recessing the head of screw 188 a below the surface of flange 182 a, thereby reducing a trip hazard.

Turning to FIG. 10, leaf spring portion 40 b of fender 10 b includes a flange 182 b that abuts a front side 34 b of mounting portion 30 b and is connected to mounting portion 30 b by means of one or more fasteners, such as a screw 188 b. Mounting along front side 34 b allows the upper sides 186 of leaf spring portion 40 b and mounting portion 10 b to be positioned flush with the top surface of structure 174, thereby extending the usable topsides area of structure 174. Screw 188 b may optionally be countersunk or otherwise recessed (not shown) below the outer surface of leaf spring portion 40 b to avoid rubbing on an impacting object.

With reference to FIG. 11, leaf spring portion 40 c of fender 10 c includes a flange 182 c that extends horizontally along upper longitudinal margin 170 and a hangar tongue 192 that extends from a proximal end of flange 182 c downwardly behind mounting portion 30 c. An elastomer layer 92 has a height that is less than mounting portion 30 c to leave a groove behind mounting portion 30 c near upper longitudinal margin 170. A transverse pair of fasteners 188 c are driven through flange 182 c and hangar tongue 192 to secure leaf spring portion 40 c to mounting portion 30 c.

In fenders 10 a-c (FIGS. 9-11), mounting portions 30 a-c are removably fastened to structure 174 with mounting fasteners 48 along the length of mounting portions 30 a-c. Leaf spring portions 40 a-c are fastened to mounting portions 30 a-c independently of the connection of mounting fasteners 48. Access openings 76 are provided in leaf spring portions 40 a-c in alignment with mounting holes 42 of mounting portions 30 a-c. The arrangement and independent connection of the leaf spring and mounting portions allows leaf spring portions 40 a-c to be detached for replacement without disturbing the connection between mounting portion 30 a-c and structure 174 or disturbing the resilient layer 92 interposed therebetween. The arrangement of access openings 76 also allows for fenders 10 a-c to be installed and removed as a unit, when desired, by uncoupling mounting fasteners 48, without detaching leaf spring portions 40 a-c from mounting portions 30 a-c.

Alternatively, as shown in FIG. 12, mounting fastener 48 can be utilized for two purposes: to attach mounting portion 30 d to structure 174 and to secure leaf spring portion 40 d to mounting portion 30 d. Similarly to fender 10 c (FIG. 11), leaf spring portion 40 d of fender 10 d includes a flange 182 d that extends in a horizontal direction from a curved portion 202 of leaf spring portion 40 d and along upper longitudinal margin 170. A tongue 206 extends downwardly from flange 182 d into a longitudinal groove 210 formed in mounting portion 30 d. Although groove tongue 206 and longitudinal groove 210 are arranged along top margin 170, alternative configurations might involve placement of tongue 206 and groove 210 in other places, such as along lower longitudinal margin 178, for example.

Longitudinal groove 210 is preferably an elongate channel that is deep enough to interrupt mounting hole 42, but may also be less deep in alternative embodiments (not shown), in which case mounting portion 30 d may include a secondary set of leaf-spring mounting holes (not shown) located adjacent mounting holes 42. Longitudinal groove 210 is preferably a generally U-shaped channel that intersects at least some of mounting holes 42 intermediately of rear side 32 d and front side 34 d of mounting portion 30 d, creating first and second upwardly extending longitudinal ribs or tines 222 and 224 between which tongue 206 extends for connecting leaf spring portion 40 d to mounting portion 30 d. Tongue 206 and tines 222 and 224 collectively form a joint 228 of fender 10 d. In an alternative embodiment (not shown) groove 206 could be formed in front side 34 d of mounting portion 30 d adjacent upper longitudinal margin 170, forming an L-shaped step. In the various embodiments described above with reference to FIG. 12, mounting hole 42 preferably opens into longitudinal groove 206.

In the preferred embodiment, one or more coupling holes 230 are formed in or drilled through tongue 206 and aligned with mounting hole 42 to receive a mounting fastener 48, which couples leaf spring portion 40 d to both mounting portion 30 d and structure 174. Coupling holes 230 may be bored through tongue 206 or may, alternatively, comprise downwardly opening notches (not shown) cut or formed into the lower edge of tongue 206. In embodiments in which coupling holes are bounded, mounting portion 30 d must be pulled away from structure 174 to detach leaf spring portion 40 d for replacement or repair. The presence of first tine 222 allows mounting portion 30 d to remain partly supported on mounting fasteners 48 when detaching leaf spring portion 40 d. In embodiments including notches along the lower edge of tongue 206, mounting fasteners 48 are merely loosened to allow tongue 206 to slide free of longitudinal groove 210 for detachment of leaf spring portion 40 d.

In each of the embodiments of fender 10 a-d shown in FIGS. 9-12, the corresponding mounting portion 30 a-d and leaf spring portion 40 a-d together form a compact P-shaped cross section that is strong, durable, and highly resilient. Any of the various materials and combinations of materials described above with reference to FIGS. 3-8 can be used in connection with the two-piece fenders 10 a-c of FIGS. 9-12. For example, in some embodiments a low cost plastic material is used for mounting portions 30 a-d and UHMWPE is used for leaf spring portions 40 a-d. In other embodiments, both the mounting portions 30 a-d and leaf spring portions 40 a-d are made of UHMWPE. Furthermore, many of the features, modifications, and accessories described above with reference to FIGS. 3-8 can be applied to fenders 10 a-d of FIGS. 9-12.

It will be obvious to those having skill in the art that many changes may be made to the details of the above-described embodiments without departing from the underlying principles of the invention. The scope of the present invention should, therefore, be determined only by the following claims. 

1. A bumper rigidly connected to a surface of a first object to thereby protect the first object from damage due to a force applied by a second object, the bumper comprising: a member having a proximate portion rigidly connected to the first object, the proximate portion extending away from the first object and transitioning into a middle portion substantially parallel to the surface of the first object, the middle portion transitioning into a distal portion, the distal portion extending toward the first object and terminating at a free end, the member thereby defining a compression space between the first object and the member; the member operable to collapse into the compression space when the second object applies a force to the member; and the middle portion having a front side facing the second object, the front side having a low coefficient of kinetic friction when the second object slides against the middle portion.
 2. The bumper of claim 1, further comprising: a base plate rigidly connected to the proximate portion of the member, the base plate having first and second opposing sides, wherein the first side faces and rigidly connects to the first object, and the distal portion of the member abuts the second side of the base plate.
 3. The bumper of claim 2, further comprising: an elastomer layer positioned between the first side of the base plate and the first object.
 4. The bumper of claim 2 wherein the base plate and the member are formed of a plastic material having a coefficient of kinetic friction against itself of between approximately 0.15 and approximately 0.25 when dry to thereby facilitate the free end of the member sliding along the second side of the base plate when the member collapses into the compression space.
 5. The bumper of claim 2 wherein the base plate includes multiple mounting holes positioned under the member for receiving mounting fasteners for mounting the bumper to the first object and the member includes multiple access openings aligned with the mounting holes, the access openings each being sized to admit a tool for tightening the mounting fasteners, to thereby facilitate attachment of the bumper to the first object.
 6. The bumper of claim 2, further comprising: a groove formed in the base plate; and a tongue extending from the member and into the groove for rigidly connecting the member to the base plate.
 7. The bumper of claim 1 wherein the member includes at least one drainage opening to allow fluids to drain from the compression space.
 8. The bumper of claim 1 wherein the bumper includes a flat upper surface positioned flush with a top side of the first object and the flat upper surface includes a slip resistant texture.
 9. The bumper of claim 1 wherein the member is formed from a hydrophobic plastic material.
 10. The bumper of claim 1 wherein the member is formed from ultra high molecular weight polyethylene.
 11. The bumper of claim 10 wherein the ultra high molecular weight polyethylene includes a pigment, an ultraviolet stabilizer, or both.
 12. The bumper of claim 1 wherein the front side of the middle portion has a coefficient of kinetic friction against dry polished steel of less than approximately 0.3.
 13. The bumper of claim 1, further comprising: a means for detachably connecting the member to the first object.
 14. A rub rail mounted to a first object to thereby protect the first object from damage due to a force applied by a second object, the rub rail comprising: a curved member having a fixed end rigidly secured to the first object and a free end opposite the fixed end; the fixed end and the free end each operable to transmit to the first object a fraction of the force from the second object; a compression space defined by the curved member and the first object and into which at least a portion of the curved member enters when the second object applies a force to the curved member; the curved member having a contact area defined by the portion of the second object that touches the curved member during operation, the member configured such that the contact area increases as a portion of the curved member enters the compression space; and the curved member being formed from a material having a low coefficient of kinetic friction as the second object slides along the curved member.
 15. The rub rail of claim 14 further comprising: a base plate rigidly connected to the proximate portion of the curved member, the base plate having first and second opposing sides, wherein the first side faces and rigidly connects to the first object, and the free end of the curved member abuts the second side of the base plate.
 16. The rub rail of claim 15 wherein the curved member is configured such that the free end slides along the second side of the base plate as the second object applies the force to the curved member and the curved member enters the compression space.
 17. The rub rail of claim 14 wherein the curved member is formed from ultra high molecular weight polyethylene.
 18. A load absorbing device, comprising: a curved member rigidly connected to a first object, the curved member having a fixed end rigidly connected to the first object and a free end opposite the fixed end; the curved member having a contact area to absorb a load delivered by a second object, the contact area increasing when under load to thereby more evenly distribute the load between the curved member and the second object; and the curved member being formed from a material having a low coefficient of kinetic friction when the second object is in contact with and moves relative to the curved member.
 19. The load absorbing device of claim 18 wherein the load absorbing device is rigidly connected to a marine vessel, a marine structure against which a marine vessel may rub or impact, or both, and the load absorbing device is for use in a marine environment.
 20. The load absorbing device of claim 18 further comprising: a base plate rigidly connected to the proximate portion of the curved member, the base plate having first and second opposing sides, wherein the first side faces and rigidly connects to the first object, and the free end of the curved member is adjacent to the second side of the base plate.
 21. The load absorbing device of claim 20 wherein the free end is spaced apart from the second side of the base plate when the curved member is in an unloaded condition.
 22. The load absorbing device of claim 20 wherein the base plate comprises an elongate strip having a longitudinal axis, the curved member comprises an elongate curved member that meets the base plate at a common joint that extends parallel to the longitudinal axis, and fixed end of the curved member extends away from the first object in a direction transverse of the longitudinal axis and transitions into a middle portion substantially parallel to a surface of the first object and the middle portion extends toward the first object and transitions into the free end.
 23. The load absorbing device of claim 20 wherein the base plate and the curved member are integrally formed of a one-piece construction.
 24. The load absorbing device of claim 18 wherein the fixed end of the curved member includes a flange that is rigidly connected to the first object via at least one fastener.
 25. The load absorbing device of claim 18 wherein the fixed end of the curved member has opposing first and second surfaces and the fixed end of the curved member includes at least one mounting hole extending through the first and second surfaces and sized to receive a mounting fastener for rigidly connecting the curved member to the first object.
 26. The load absorbing device of claim 18 wherein the curved member is formed from ultra high molecular weight polyethylene. 